More frequently, optical input/output (I/O) is being used in computer systems to transmit data between system components. Optical I/O is able to attain higher system bandwidth with lower electromagnetic interference than conventional I/O methods. In order to implement optical I/O, optical transceivers transmit and receive radiant energy to/from a waveguide, such as optical fibers.
However, in an optical transceiver circuit, the most encountered problem is the selection of preamplifier bandwidth. If the preamplifier (e.g., trans-impedance amplifier (TIA)) has too much bandwidth, the optical sensitivity and gain on the jitter performance will be degraded. Nevertheless, the optical sensitivity can be improved by reduce the bandwidth of TIA. Therefore, most designers pursue optimizing the bandwidth according to the different data rates. Typically, the TIA is designed to have a bandwidth of 0.7*bit rate.
Current ROSA (Receiver optical sub assembly) typically have five output pins (Vcc, GND, out+, out− and RSSI (receiver signal strength indication)). The RSSI pin is designed to generate the current output proportional to the received optical signal. Thus, there is no pin to select the bandwidth in the TIA inside the ROSA.